The prior art has provided a great variety of different bracket structures for attachment to a tooth with the brackets having structure for accommodating torque imparting wires of various shapes as well as other appliances to apply torque or appropriate force to a tooth to reposition the tooth to improve appearance, bite or to repair damage resulting from accident. In current orthodontic appliances, these brackets may be attached to the teeth directly by means of acid etched bonded adhesives with the forces imparted resulting from the use of metal archwires of various dimensions, alloys and designs. To accommodate the widest variety of different orthodontic problems, the brackets of the prior art have an enormous range of design configurations believed necessary to enable a practitioner to impart specific treatment effects to a patient.
In current orthodontic practice, four types of appliances are in common usage. Of these, the most common include the edgewise appliance, the Begg appliance, the straight wire appliance, and the combination appliance. The introduction of these appliances commenced early this century and continues up to the present day. Of these, the most frequently used are the standard edgewise bracket or the straight wire type of bracket. The acceptance of these two alternatives is due primarily to the ability to simplify control of the tooth in three dimensions. The success of the edgewise or straight wire type of appliance also is believed due to the ability of the archwire slot to automatically produce movements facio-lingually, mesiodistally and axially without special bends in the archwire. This particular appliance is well known for its translatory type of movement and its precision and control.
The Begg type of appliance, such as represented by U.S. Pat. Nos. 3,128,553 of Apr. 14, 1964 and 3,163,933 of Jan. 5, 1965, are generally understood as imparting simple tipping to the tooth without any three dimensional control of any applied forces. It has been characterized by the use of a narrow bracket of the ribbon type which, in its early design, was opened at the incisal end and, in later designs, at the gingival area of the tooth. A retaining pin was employed to retain the archwire in position when a light archwire was employed. In many cases, auxiliary appliances such as springs and wires were required to correct excessive tipping or torquing of the tooth and to coordinate the crown and root position of the teeth.
The combination bracket involves an attempt to combine the edgewise and Begg type of brackets into one structure. With several modifications to accommodate different types of wires or combination of wires, the combination bracket permitted the use of translatory movements in a facial edgewise slot and tipping in either the gingival or incisal Begg slot.
Straight wire orthodontic appliances have been widely accepted in addition to the edgewise techniques as they have been associated with simplified mechanics, arch formation and more precision in finishing procedures. Unfortunately, a number of inherent problems have arisen which have adversely affected their treatment effectiveness. To a large extent, the imparting of a directional force or vector to a tooth depends on the shape and positioning of a rectangular slot in the bracket which receives a complimentary shaped wire. For the manufacturer and the practitioner, however, the requirement of maintaining a large inventory of differently angulated rectangular slots has proven undesirable in view of the expense involved and the difficulty of properly installing such highly selectively employed brackets in patients. As a consequence, manufacturers have endeavored to manufacture a bracket capable of producing regular three dimensional tooth movement but structured so as to accommodate an average tooth anatomy.
Unfortunately, due to the high variability of human tooth anatomy, such brackets have not met with widespread acceptance thus forcing manufacturers to produce several different types of brackets for specific tooth anomalies. This has resulted in the necessity for a practitioner maintaining a wide variety of different brackets in his inventory thereby increasing his costs and that of the patient.
Another difficulty constraining the designers of brackets in this field is the requirement of securing the archwire to the bracket in an effective and safe manner that is comfortable for the patient. In some designs, a compromise has been reached between ease of attachment of the archwire to the bracket and the effectiveness of the bracket in treating the tooth abnormality of the patient.
Additionally, edgewise and straight wire brackets are designed so teeth cannot freely move by tipping. The restriction on tipping movement slows the movement, increases treatment time, increases the forces required and frequently causes an increase in pain and discomfort for the patient. A bracket designed to permit tipping overcomes these disadvantages.